linux-kernel - [PATCH v2 12/23] powerpc: allow pte_offset_map[

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Message-ID: <54c8b578-ca9-a0f-bfd2-d72976f8d73a@google.com>
Date:   Thu, 8 Jun 2023 12:23:35 -0700 (PDT)
From:   Hugh Dickins <hughd@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
cc:     Mike Kravetz <mike.kravetz@...cle.com>,
        Mike Rapoport <rppt@...nel.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Matthew Wilcox <willy@...radead.org>,
        David Hildenbrand <david@...hat.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Qi Zheng <zhengqi.arch@...edance.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Greg Ungerer <gerg@...ux-m68k.org>,
        Michal Simek <monstr@...str.eu>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Helge Deller <deller@....de>,
        John David Anglin <dave.anglin@...l.net>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Alexandre Ghiti <alexghiti@...osinc.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
        "David S. Miller" <davem@...emloft.net>,
        Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>, x86@...nel.org,
        linux-arm-kernel@...ts.infradead.org, linux-ia64@...r.kernel.org,
        linux-m68k@...ts.linux-m68k.org, linux-mips@...r.kernel.org,
        linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH v2 12/23] powerpc: allow pte_offset_map[_lock]() to fail

In rare transient cases, not yet made possible, pte_offset_map() and
pte_offset_map_lock() may not find a page table: handle appropriately.
Balance successful pte_offset_map() with pte_unmap() where omitted.

Signed-off-by: Hugh Dickins <hughd@...gle.com>
---
 arch/powerpc/mm/book3s64/hash_tlb.c     | 4 ++++
 arch/powerpc/mm/book3s64/subpage_prot.c | 2 ++
 arch/powerpc/xmon/xmon.c                | 5 ++++-
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/mm/book3s64/hash_tlb.c b/arch/powerpc/mm/book3s64/hash_tlb.c
index a64ea0a7ef96..21fcad97ae80 100644
--- a/arch/powerpc/mm/book3s64/hash_tlb.c
+++ b/arch/powerpc/mm/book3s64/hash_tlb.c
@@ -239,12 +239,16 @@ void flush_hash_table_pmd_range(struct mm_struct *mm, pmd_t *pmd, unsigned long
 	local_irq_save(flags);
 	arch_enter_lazy_mmu_mode();
 	start_pte = pte_offset_map(pmd, addr);
+	if (!start_pte)
+		goto out;
 	for (pte = start_pte; pte < start_pte + PTRS_PER_PTE; pte++) {
 		unsigned long pteval = pte_val(*pte);
 		if (pteval & H_PAGE_HASHPTE)
 			hpte_need_flush(mm, addr, pte, pteval, 0);
 		addr += PAGE_SIZE;
 	}
+	pte_unmap(start_pte);
+out:
 	arch_leave_lazy_mmu_mode();
 	local_irq_restore(flags);
 }
diff --git a/arch/powerpc/mm/book3s64/subpage_prot.c b/arch/powerpc/mm/book3s64/subpage_prot.c
index b75a9fb99599..0dc85556dec5 100644
--- a/arch/powerpc/mm/book3s64/subpage_prot.c
+++ b/arch/powerpc/mm/book3s64/subpage_prot.c
@@ -71,6 +71,8 @@ static void hpte_flush_range(struct mm_struct *mm, unsigned long addr,
 	if (pmd_none(*pmd))
 		return;
 	pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
+	if (!pte)
+		return;
 	arch_enter_lazy_mmu_mode();
 	for (; npages > 0; --npages) {
 		pte_update(mm, addr, pte, 0, 0, 0);
diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 70c4c59a1a8f..fae747cc57d2 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -3376,12 +3376,15 @@ static void show_pte(unsigned long addr)
 	printf("pmdp @ 0x%px = 0x%016lx\n", pmdp, pmd_val(*pmdp));
 
 	ptep = pte_offset_map(pmdp, addr);
-	if (pte_none(*ptep)) {
+	if (!ptep || pte_none(*ptep)) {
+		if (ptep)
+			pte_unmap(ptep);
 		printf("no valid PTE\n");
 		return;
 	}
 
 	format_pte(ptep, pte_val(*ptep));
+	pte_unmap(ptep);
 
 	sync();
 	__delay(200);
-- 
2.35.3